Although recent epidemiologic evidence has demonstrated that obstructive sleep apnea increases significantly in prevalence among women after the menopausal transition, existing research has not yet elucidated the underlying mechanisms. The goal of this project is to elucidate the relationships between declining hormone levels in perimenopausal women, changes in upper airway structure and function, and the development of sleep-disordered breathing. To do so, we propose to perform a longitudinal study of women going through the menopausal transition that will examine changes in the severity of sleep- disordered breathing, upper airway soft tissue structures and upper airway collapsibility. Unlike retrospective or cross-sectional studies, this prospective study design will allow us to chronicle changes within subjects over time due to hormonal changes, while controlling for confounding factors including weight gain, age and time. The aims of the proposed study are: 1) To determine the relationship between reproductive hormone levels (estradiol, progesterone and testosterone) and change in sleep-disordered breathing; 2) To assess changes in upper airway anatomy and fat distribution over the menopausal transition and examine their relationship to hormone levels and sleep-disordered breathing; and 3) To determine changes in airway collapsibility over the menopausal transition. To accomplish these aims, we will recruit subjects from the Penn Ovarian Aging Study (PDAS), an ongoing prospective study of the menopausal transition in over 300 African-American and Caucasian women from Philadelphia with nearly 10 years of previously collected hormonal and other data, for new data collected yearly by home polysomnography and other procedures. We believe this study is likely to identify how reproductive levels' lead to specific changes in upper airway structure and function, precipitating the development of obstructive sleep apnea. These findings will allow us to identify women at risk for sleep-disordered breathing after menopause and to focus on tailoring treatments in this area. [unreadable] [unreadable] [unreadable]